## **Core Concept**
The question tests knowledge of antiviral medications, specifically those used to treat influenza, and their routes of administration. Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza viruses. Antiviral drugs are crucial in managing and preventing the spread of the flu.

## **Why the Correct Answer is Right**
Zanamivir (Relenza) and oseltamivir (Tamiflu) are two well-known antiviral drugs used to treat and prevent influenza A and B. Among these, **Zanamivir** is specifically administered via inhalation. It works by inhibiting the neuraminidase enzyme on the surface of influenza viruses, preventing the release of new viral particles from infected cells. This mechanism is critical for limiting the spread of the virus within the body.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Oseltamivir is given orally, not through inhalation. It also inhibits the neuraminidase enzyme but does so after being absorbed into the bloodstream following oral administration.
- **Option B:** This option might seem plausible but is not specified; however, assuming it refers to another antiviral, the focus here is on inhalation route specificity which aligns with Zanamivir.
- **Option D:** Without a specific drug mentioned, it's hard to directly refute, but given the context, the emphasis is on identifying which drug is administered via inhalation.

## **Clinical Pearl / High-Yield Fact**
A critical point to remember is that **Zanamivir (Relenza)** is administered via inhalation and is particularly useful for patients who cannot tolerate oral medications or have gastrointestinal issues. It's also essential to note that Zanamivir can cause bronchospasm, especially in patients with underlying respiratory conditions like asthma.

## **Correct Answer:** B. Zanamivir.